Method for producing a dielectric material on a semiconductor device and semiconductor device

ABSTRACT

Method for producing a dielectric material on a semiconductor device and semiconductor device 
     Method for producing a dielectric material on semiconductor device with an atomic layer deposition procedure, whereby an aluminum oxide nitride or a silicon oxide nitride or an aluminum silicon oxide nitride layer is deposited comprising a rare earth metal-element. 
     The invention describes a semiconductor device with a dielectric layer comprising aluminum oxide nitride or silicon oxide nitride or an aluminum silicon oxide nitride comprising a rare earth metal element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention refers to a method for producing a dielectricmaterial on a semiconductor device and producing a semiconductor devicewith a dielectric material for example a DRAM memory. For differenttechnical solutions it is an advantage to use a dielectric material in asemiconductor device that comprises a high dielectric constant. Thedielectric layer with a high dielectric constant may be used in atransistor or in a capacitor of a semiconductor device, for example asemiconductor memory.

2. Description of the Related Art

In the state of the art several methods are known for producing adielectric layer on a semiconductor device. For example it is known bythe US patent application US 2004/0198069 A1 a method for forming alayer comprising hafnium on a substrate surface sequentially exposingthe substrate surface to a hafnium precursor to form a hafnium layer ona substrate surface; reacting a second precursor with the hafniumcontaining layer; reacting a third precursor with the hafnium containinglayer; reacting a fourth precursor with the hafnium containing layer.The deposited compound film comprises hafnium and at least threeelements selected from the group consisting of silicon, aluminum, oxygenand nitrogen. The deposited dielectric layer can be realised as ahafnium silicon oxinitride and a hafnium aluminum oxygen nitride,hafnium silicon aluminum nitride and hafnium silicon aluminum oxidenitride.

Furthermore it is known to produce a laminate gate dielectric in a SiMOSFET with nitrogen incorporated in a hafnium oxide aluminum oxidelaminate by Hyung-Seok Jung et al., in “Improved Current Performance ofCMOSFETs with Nitrogen Incorporated HfO2-Al2O3 Laminate GateDielectric”, IEDM Tech. Dig. (2002), pages 853-856.

Furthermore it is known by Masato Koyama et al., in “Effect of FilmComposition of Nitrogen Incorporated Hafnium Aluminate Gate Dielectricon Structural Transformation and Electrical Pproperties throughHigh-Temperature Annealing”, Japanese Journal of Applied Physics, volume43, No. 4B, 2004, pages 1788-1794, to use a nitrogen incorporatedhafnium aluminate gate dielectric layer as a high k-material for a SIMOSdevice.

Furthermore it is known by Katsuyuki Sekine et al., in “Nitrogen ProfileControl by Plasma Nitridation Technique for Poly-Si Gate HfSiON CMOSFETwith Excellent Interface Property and Ultra-low Leakage Current”, IEDMTech. Dig. (2003), pages 102-106, to use a poly-silicon gate on hafniumsilicon oxynitride for a SiMOS field-effect transistor.

Furthermore it is known by Masahiro Koike et al., in “Effect of Hf—NBond on Properties of Thermally Stable Amorphous HfSiON andApplicability of this Material to Sub-50 nm Technology Node LSIs”, IEDMTech. Dig. (2003), pages 107-110, to use hafnium silicon oxinitride asan ultra thin layer with high hafnium and high nitride concentration asa high k material.

In the field of semiconductor processing, memory device processing orother electronic device processing, atomic layer deposition is used fordepositing high k material. As electronic devices continue to shrink andthe density of devices continues to increase, the size and aspect ratioof the features are becoming more important with a high impact in thequality of the semiconductor device. Although there are differentmethods for producing a dielectric material with a high k-constant,there is furthermore a need for a method for depositing dielectricmaterial with a high k-constant.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is a method for producing adielectric material on a semiconductor device with an atomic-layerdeposition procedure, whereby an aluminum oxide nitride or a siliconoxide nitride layer or an aluminum silicon oxide nitride is depositedcomprising an element of the rare earth metals. The rare earth metalshave in combination with the aluminum oxide nitride or the silicon oxidenitride or the aluminum silicon oxide nitride the advantage to provide adielectric layer with a high dielectric k-constant and with suitablecharacteristics that are necessary for semiconductor processingespecially for arrangements with a high density of semiconductor devicesand a high aspect ratio especially for semiconductor memories.

In another embodiment, the present invention is a method for producing adielectric material on the semiconductor device with an atomic layerdeposition, whereby a first layer comprises aluminum oxide, a secondlayer comprises aluminum nitride, a third layer comprises a rare earthmetal oxide and a fourth layer comprises a rare earth metal nitride. Thecombination of these four layers leads to a dielectric material thatcould be easily produced and has suitable mechanical and chemicalproperties for different semiconductor devices for example forsemiconductor memories or semiconductor transistors.

In a further embodiment of the invention the dielectric materialcomprises a first layer of silicon oxide, a second layer of siliconnitride, a third layer of a rare earth metal oxide and a fourth layer ofa rare earth metal nitride. Also this combination of layers is ofadvantage for producing a dielectric material. This dielectric materialcan easily be produced and has advantageous mechanical and chemicalproperties.

In a further embodiment of the invention the dielectric materialcomprises a first layer of silicon oxide, a second layer of siliconnitride, a third layer of aluminum oxide, a fourth layer of aluminumnitride, a fifth layer of a rare earth metal oxide and a sixth layer ofa rare earth metal nitride. Also this combination of layers is ofadvantage for producing a dielectric material. This dielectric materialcan easily be produced and has advantageous mechanical and chemicalproperties.

In another embodiment the aluminum oxide nitride layer comprises morethan 30 percent by weight of nitrogen.

In a further embodiment of the invention the aluminum oxide nitridelayer comprises less than 50 percent by weight of the rare earthmetal-element.

In another embodiment of the invention the silicon oxide nitride layercomprises more than 20 percent by weight of nitrogen.

Furthermore a dielectric material with good chemical, mechanical andelectrical properties can be attained by using a silicon oxide nitridelayer comprising more than 30 percent by weight of a rare earthmetal-element.

In a further embodiment the semiconductor surface is prepared using athermal nitride process or a plasma nitride process or a nitrideimplantation process. The preparation of the surface improves thequality of the dielectric material layer that is deposited by the atomiclayer deposition on the semiconductor surface.

In a further embodiment of the invention a starting layer consisting ofa rare earth metal is deposited before the dielectric material. Thestarting layer improves the deposition quality of the dielectricmaterial.

Furthermore as a rare earth metal one element of the lanthanides orscandium or yttrium is used. With these elements a good quality of thedielectric material is attained.

In a further embodiment the invention relates to a semiconductor devicecomprising a dielectric material made of aluminum oxide nitride orsilicon oxide nitride or aluminum silicon oxide nitride comprising anelement of the rare earth metals.

In another embodiment a semiconductor memory with a capacitor isprovided, whereby the capacitor comprises a dielectric material withaluminum oxide nitride or silicon oxide nitride or aluminum siliconoxide nitride comprising one element of the rare earth metals. Thisdielectric material has good electrical, mechanical and chemicalproperties and can be used for a structure with high aspect ratios.

In a further embodiment of the invention the dielectric material is usedin a semiconductor device comprising a transistor, whereby thedielectric material constitutes a layer of the transistor.

The present invention is based on the idea to propose a dielectricmaterial for a semiconductor device with improved electrical, chemicaland/or mechanical properties. This object is attained by a dielectricmaterial with an aluminum oxide nitride or a silicon oxide nitride or analuminum silicon oxide nitride layer comprising an element of the rareearth metals. This dielectric material has a high dielectric constant k,can easily be deposited by an atomic layer deposition and has preferablemechanical, electrical and/or chemical properties. With this dielectricmaterial especially transistors or capacitors for example insemiconductor memories can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description taken in conjunction withthe accompanying drawings in which:

FIG. 1 is a sectional view of a semiconductor device at a first processstep,

FIG. 2 is a sectional view of the semiconductor device at a secondprocess step,

FIG. 3 is a sectional view of the semiconductor device at a thirdprocess step,

FIG. 4 is a sectional view of the semiconductor device at a fourthprocess step,

FIG. 5 a sectional view of a dielectric material with four layers, and

FIG. 6 a sectional view of a dielectric material with six layers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides methods for producing a dielectricmaterial on a semiconductor device using an atomic layer depositionprocedure with an aluminum oxide nitride or a silicon oxide nitridelayer or aluminium silicon oxide nitride comprising a rare earth metal.Furthermore the present invention provides semiconductor devicescomprising a dielectric material comprising an aluminum oxide nitride ora silicon oxide nitride or a aluminium silicon oxide nitride layercomprising a rare earth metal.

The inventive method and the inventive semiconductor device areexplained with the example of a capacitor in a semiconductor substrate.The capacitor is for example a part of a memory cell of a memory device.The method and the dielectric material could also be used in atransistor of a semiconductor device for example in a memory device orin any other semiconductor devices with a dielectric material.

For producing the dielectric material on the semiconductor device theatomic layer deposition is used whereby a metal aluminum oxide nitrideor a metal silicon oxide nitride or a metal aluminium silicon oxidenitride dielectric material is produced. As a metal one of the rareearth elements is used. As a rare earth metal (=RE) basically theelements lanthanides, scandium or yttrium could be used. The lanthanidescomprise Lanthanum, Cerium, Praseodymium, Neodymium, Promethium,Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium,Thulium, Ytterbium and Lutetium. To produce the aluminum oxide nitridelayer comprising a rare earth metal four depositing process steps whereused.

In the first step a rare earth metal oxide is deposited to produce anoxygen rare earth metal connection. In a second deposition process analuminum oxide is deposited to produce an aluminum oxygen connection. Ina third deposition process aluminum nitride is deposited providing analuminum nitride connection. Furthermore a rare earth metal nitride isdeposited to provide a rare earth metal nitride connection.

For the deposition of the rare earth metal different precursors may beused during the atomic layer deposition. A first group of precursors areconstituted by amidinates: RE (R/amd) 3, whereby R equals iPr(iso-propyl) or tBu (tert-butyl) etc. and amd equals azetamidinato.

A second group of precursors are constituted by alkoxides:

-   RE(OR)₃, RE(OR)×(mmp)_(3-x) with R=tBu, iPr, Me, . . . and    mmp=1-methoxy-2methyl-2-propa-nolate (MeOMeCHCH₂OMe)

A third group of the precursors are constituted by cyclopentadienyle:

-   RE-   (Cp)₃, RE(CpCH₃)₃, RE(CH₃)(Cp)₂, . . . with Cp=C₅H₅ or C₅MeH₄ or    C₅EtH₄ or C₅Me₅ or C₅iPr₃H₂.

A fourth group of precursers for depositing the rare earth metal istetramethylheptane-3,5-dionate compounds:

-   RE(thd)₃ with thd=2,2,6,6-tetramethylheptane-3,5-dionate.

Atomic layer deposition (ALD) utilizes sequential precursor gas pulsesto deposit a film one layer at a time. As a basic process, as firstprecursor gas is introduced into the process chamber and produces amonolayer of gas on the wafer surface. A second precursor of gas is thenintroduced into the chamber reacting with the first precursor to producea monolayer of film on the wafer surface. Since each pair of gas pulses(one cycle) produces exactly one monolayer of film the thickness of theresulting film may be precisely controlled by the number of depositioncycles.

The whole deposition of the dielectric material of the semiconductordevice comprises several repetitions of an at least four-step-processwith one of the following embodiments: In the first embodiment thefirst, the second, the third and the fourth deposition process step isrepeated several times until a predetermined thickness of the dielectricmaterial is attained.

In a second embodiment the first, the second, the third and the fourthdeposition process steps are repeated several times with differentnumbers of repetitions for each process step. This means that eachprocess step may be repeated directly a predetermined number until thefollowing deposition process step is done. The deposition process stepsmay be initiated in different order.

In one embodiment the atomic layer deposition process starts withaluminum oxide or aluminum nitride layer to get a good basis fordepositing the dielectric material. In a further embodiment the surfaceof the semiconductor device is prepared before starting the atomic layerdeposition process with a thermal nitration using NH₃ or a plasmanitration or a nitride implantation is used to produce a better surfacefor the atomic layer deposition procedure of the dielectric material.

Due to the atomic layer deposition process as discussed above it ispossible to change the composition of the individual elements forexample the composition of the rare earth metal within the thickness ofthe dielectric material. Depending on the embodiment it might be anadvantage to change the composition starting with a higher percentage ofaluminum and changing along the thickness of the dielectric material toa higher percentage of the rare earth metal. Furthermore it may be anadvantage to start with a higher concentration of oxygen and changewithin the thickness of the dielectric material to a higherconcentration of nitrogen.

Furthermore the aluminum oxide nitride rare earth metal layer comprisesmore than 30 percent by weight of nitrogen. In another embodiment therare earth metal aluminum oxide nitride comprises less than 50% of rareearth metal. Preferably the deposited dielectric material is coveredwith a cover layer before starting a thermal process to prevent adiffusion of nitrogen. Due to the atomic layer deposition process a goodcovering of rim areas is possible also on a structure with a high aspectratio.

In a further embodiment instead of aluminum oxide and aluminum nitridealso silicon oxide and silicon nitride may be used. In this embodiment arare earth metal silicon oxide nitride layer is deposited.

In a further embodiment also aluminum oxide, aluminum nitride, siliconoxide and silicon nitride may be used. In this embodiment a rare earthmetal silicon aluminum oxide nitride layer is deposited.

Furthermore the surface of the semiconductor device might be prepared bydepositing a starting layer comprising silicon oxide or silicon nitride.This preparation improves the quality of the deposited dielectricmaterial layer.

The rare earth metal silicon oxide nitride layer comprises in a furtherembodiment more than twenty percent by weight of nitrogen. The furtherembodiment the rare earth metal silicon oxide nitride layer comprisesmore than thirty percent by weight of the rare earth metal.

In a further embodiment a rare earth metal silicon aluminum oxidenitride layer is deposited.

The rare earth metal silicon aluminum oxide nitride layer comprises in afurther embodiment more than twenty percent by weight of nitrogen. In afurther embodiment the rare earth metal silicon aluminium oxide nitridelayer comprises more than thirty percent by weight of the rare earthmetal.

The dielectric material could be used in all technical embodiments thatuse a dielectric layer with a high dielectric constant k.

The FIGS. 1 to 4 depict some process steps that are used producing atrench capacitor as an example for a memory cell of a memory device.

FIG. 1 depicts a sectional view of a semiconductor substrate thatconsists of semiconductor material for example silicon or gallium. Inthe semiconductor substrate 1 a deep trench 2 with a collar rim 3 isprocessed. The collar rim consists for example of silicon oxide. In acleaning process the surface of the collar rim 3 and of the deep trench2 is cleaned for example with wet chemical solutions. Then the surfacemay be conditioned with a rapid thermal processing.

The upper surface of the substrate 1 is covered with a cover layer 4.The cover layer 4 is made of silicon nitride in this embodiment.

Then a thin metal layer 5 is deposited on the surface of a bottle region8 of the deep trench 2. The thickness of the metal layer 5 may be in theregion of 5 nm. The metal layer constitutes a starting layer 5 thatcomprises a rare earth metal. After this the dielectric material 6 isdeposited by the atomic layer deposition process as discussed above. Thedielectric layer 6 covers the deep trench, the collar rim and thesurface of the substrate. The atomic layer deposition is processed asdescribed above.

Then in a further process step a conducting layer 7 is deposited on thesurface of the deep trench, filling up the opening of the deep trench.This process step is shown in FIG. 1. As a metal material for theconducting layer 7 titanium nitride may be used.

In a following process the conducting layer 7 is removed from thesurface of the substrate 1 and the surface of the collar rim 3. In abottle region 8 of the deep trench the conducting layer 7 remains on thesurface of the deep trench 2. This process step is shown in FIG. 2.

In a following process step the dielectric layer 6 is removed from thecollar rim 3 and the upper surface of the substrate 1. The dielectriclayer 6 remains on the surface of the bottle region 8 of the deep trench2.

Then the deep trench 2 is filled up with a second conducting layer 9.The second conducting layer 9 may consist of poly silicon. Depending onthe embodiment also other conducting materials might be used. Thisprocess step is shown in FIG. 3.

After this the second conducting layer 9 is removed from the uppersurface 10 of the substrate and from an upper region 11 of the collarrim 3. This process step is shown in FIG. 4, that depicts a capacityarrangement with a first and second electrode constituted by thestarting layer 5 and the conducting layer 7. Between the two electrodesthe dielectric layer 6 is arranged that is made of the dielectricmaterial.

FIG. 5 depicts a sectional view of the dielectric material 6 comprisingfour layer 12, 13, 14, 15. The four layers consist in one embodiment ofan aluminum oxide layer, one aluminum nitride layer, a rare earth metaloxide layer and a rare earth metal nitride layer.

In another embodiment the four layers of the dielectric material consistof a silicon oxide layer, a silicon nitride layer, a rare earth metaloxide layer and a rare earth metal nitride layer.

FIG. 6 depicts another embodiment of the dielectric material 6,consisting of a first, a second, a third, a fourth, a fifth and a sixthlayer 12, 13, 14, 15, 16, 17. The six layers of the dielectric materialconsist of a silicon oxide layer, a silicon nitride layer, an aluminumoxide layer, an aluminum nitride layer, a rare earth metal oxide layerand a rare earth metal nitride layer.

The position of the single layers within the layer arrangements of FIGS.5 and 6 may change depending on the embodiment.

REFERENCE LIST

-   -   1 substrate    -   2 deep trench    -   3 collar rim    -   4 cover layer    -   5 starting layer    -   6 dielectric layer    -   7 conducting layer    -   8 bottle region    -   9 second conducting layer    -   10 upper surface    -   11 upper region    -   12 first layer    -   13 second layer    -   14 third layer    -   15 fourth layer    -   16 fifth layer    -   17 sixth layer

1. A semiconductor memory comprising: a dielectric layer comprisingaluminum oxide nitride and a rare earth metal element; and a storagecapacitor, wherein the dielectric layer forms a dielectric of thestorage capacitor, wherein the dielectric layer comprises at least fourdifferent layers deposited by an atomic layer deposition process,wherein the at least four different layers comprise: a first layercomprising an aluminum oxide, a second layer comprising an aluminumnitride, a third layer comprising a rare earth metal oxide and a fourthlayer comprising a rare earth metal nitride.
 2. The semiconductor memoryaccording to claim 1, whereby a fifth layer comprises a silicon oxide, asixth layer comprises a silicon nitride.
 3. The semiconductor memoryaccording to claim 1, further comprising a transistor, whereby thedielectric material constitutes a dielectric layer of the transistor. 4.A semiconductor device comprising: a transistor with a dielectric layer,wherein the dielectric layer comprises aluminum silicon oxide nitrideand a rare earth metal element, wherein the dielectric layer comprisesat least four different layers deposited by an atomic layer depositionprocess, wherein the at least four different layers comprise: a firstlayer comprising an aluminum oxide, a second layer comprising analuminum nitride, a third layer comprising a rare earth metal oxide anda fourth layer comprising a rare earth metal nitride.
 5. Thesemiconductor device according to claim 4, wherein the dielectric layercomprises at least two additional different layers deposited by anatomic layer deposition process and wherein the at least two additionaldifferent layers comprise: a fifth layer comprising a silicon oxide anda sixth layer comprising a silicon nitride.
 6. The semiconductor deviceaccording to claim 4, further comprising a capacitor, wherein thedielectric material constitutes a dielectric layer of the capacitor. 7.A semiconductor memory comprising: a dielectric layer comprisingaluminum oxide nitride and a rare earth metal element; and a capacitor,wherein the dielectric layer forms a dielectric of the capacitor,wherein the dielectric layer comprises at least four different layersdeposited by an atomic layer deposition process, and wherein the atleast four different layers comprise: a first layer comprising a siliconoxide, a second layer comprising a silicon nitride, a third layercomprising a rare earth metal oxide and a fourth layer comprising a rareearth metal nitride.
 8. The semiconductor memory according to claim 7,whereby a fifth layer comprises an aluminum oxide and a sixth layercomprises an aluminum nitride.
 9. The semiconductor memory according toclaim 7, further comprising a transistor, whereby the dielectricmaterial constitutes a dielectric layer of the transistor.
 10. Asemiconductor device comprising: a transistor with a dielectric layer,wherein the dielectric layer comprises aluminum silicon oxide nitrideand a rare earth metal element, wherein the dielectric layer comprisesat least four different layers deposited by an atomic layer depositionprocess, wherein the at least four different layers comprise: a firstlayer comprising a silicon oxide, a second layer comprising a siliconnitride, a third layer comprising a rare earth metal oxide and a fourthlayer comprising a rare earth metal nitride.
 11. The semiconductordevice according to claim 10, wherein the dielectric layer comprises atleast two additional different layers deposited by an atomic layerdeposition process and wherein the at least two additional differentlayers comprise: a fifth layer comprising an aluminum oxide and a sixthlayer comprising an aluminum nitride.
 12. The semiconductor deviceaccording to claim 10, further comprising a capacitor, wherein thedielectric material constitutes a dielectric layer of the capacitor.